Transmission line using a power combiner for high data rate communication in a computerized tomography system

Abstract

A computerized tomography (CT) system includes a stationary frame, an annular rotating frame and apparatus that includes a phase splitter for supplying first and second modulated carrier constituents being 180° out-of-phase between one another while maintaining a uniform amplitude over the bandwidth for the modulated carrier. A transmission line is attached to the rotating frame and is positioned around the annular rotating frame. The transmission line comprises individual segments having first and second conductors respectively coupled to the he phase splitter to receive the first and second modulated carrier constituents. A coupler is attached to the stationary frame and is positioned sufficiently near the transmission line for establishing radio coupling therebetween to receive the first and second modulated carrier constituents being applied to any individual segment. The apparatus further includes a power combiner having first and second input ports for receiving the first and second modulated carrier constituents supplied by the coupler. The power combiner is designed for combining the 180° out-of-phase first and second modulated carriers to form a combined modulated carrier supplied through an output port of the power combiner. The power combiner preferably includes matching resistors for cancelling any in-phase input signals which can be received through the first and second input ports of the power combiner due to externally-generated electromagnetic interference.

What is claimed is: 
     
       1. A computerized tomography system comprising: a stationary frame;   a generally annular rotating frame;   a phase splitter having an input port coupled to receive a modulated carrier having a predetermined bandwidth, said phase splitter having first and second output ports for supplying, respectively, first and second modulated carrier constituents having a substantially 180° out-of-phase angle between one another while maintaining a substantially uniform amplitude over said bandwidth;   a transmission line attached to said rotating frame and positioned substantially around said annular rotating frame, said transmission line comprising at least one individual segment having first and second conductors respectively coupled to the first and second output ports of said phase splitter to receive the first and second modulated carrier constituents from said phase splitter;   a coupler attached to said stationary frame and being positioned sufficiently near said transmission line for establishing radio coupling therebetween to receive the first and second modulated carrier constituents being applied to said at least one individual segment; and   a power combiner having first and second input ports for receiving, respectively, the first and second modulated carrier constituents supplied by said coupler, said power combiner being adapted for combining the substantially 180° out-of-phase first and second modulated carrier constituents to form a combined modulated carrier supplied through an output port of said power combiner.   
     
     
       2. The computerized tomography system of claim 1 wherein said power combiner comprises: a first transmission line coupled to the first input port of said power combiner for supplying a respective output signal having a phase angle substantially in-phase with respect to the modulated carrier constituent received through said first input port;   a second transmission line adapted to provide a predetermined level of inductance between the second input port of said power combiner and a predetermined electrical ground, said second transmission line including reversing means coupled to the second output port for supplying a respective output signal having a phase angle substantially 180° out-of-phase with respect to the modulated carrier constituent received though said second input port; and   a combining network comprising first and second combining resistors each having one respective terminal thereof coupled in parallel to the output port of said power combiner, said first and second combining resistors each having another respective terminal respectively coupled to the first and second transmission lines for receiving, respectively, the output signals from the first and second transmission lines.   
     
     
       3. The computerized tomography system of claim 2 further comprising a compensating coil coupled between the first input port of said power combiner and said predetermined electrical ground. 
     
     
       4. The computerized tomography system of claim 2 wherein said combining network further comprises resistor means for substantially canceling any substantially in-phase input signals received at the first and second input ports of said power combiner. 
     
     
       5. The computerized tomography system of claim 4 wherein said resistor means comprises a first matching resistor having one respective terminal thereof coupled between the first transmission line and the first combining resistor, said resistor means further comprising a second matching resistor having one respective terminal thereof coupled between the second transmission line and the second combining resistor, said first and second matching resistors each having another respective terminal thereof coupled to said predetermined electrical ground. 
     
     
       6. The computerized tomography system of claim 2 wherein said first and second transmission lines each comprises a respective coaxial line having a substantially similar electrical length relative to one another. 
     
     
       7. The computerized tomography system of claim 6 wherein each of said coaxial lines comprises a flexible coaxial line wound to form a substantially cylindrical winding. 
     
     
       8. The computerized tomography system of claim 6 wherein said reversing means comprises the outer shield and the center conductor of the coaxial line for said second transmission line, said center conductor being connected to said predetermined electrical ground while said outer shield is connected to the second input port of said power combiner to receive the second modulated carrier constituent. 
     
     
       9. The computerized tomography system of claim 2 wherein said first and second transmission lines comprises a first printed-circuit stage including a respective pair of substantially corresponding conductive strips for each of said transmission lines, respective ones of the conductive strip pairs being disposed on mutually opposite surfaces of a first substrate. 
     
     
       10. The computerized tomography system of claim 7 wherein said first and second transmission lines further comprises a second printed-circuit stage including a respective pair of substantially corresponding coils for each of said transmission lines, each respective one of the coil pairs being coupled to a respective one of the conductive strips in said first stage and being disposed on mutually opposite surfaces of a second substrate. 
     
     
       11. The computerized tomography system of claim 10 wherein each of said mutually opposite surfaces on said second substrate is positioned substantially perpendicular relative to the mutually opposite surfaces on said first substrate. 
     
     
       12. The computerized tomography system of claim 9 wherein said reversing means comprises a feedthrough connector adapted to invert signal flow across each respective one of the pair of substantially corresponding strips for said second transmission line. 
     
     
       13. The computerized tomography system of claim 12 wherein said first and second transmission lines each has a substantially similar electrical length relative to one another. 
     
     
       14. The computerized tomography system of claim 2 wherein the transmission line attached to said rotating frame further comprises additional individual segments each having respective first and second conductors coupled to receive respective first and second modulated carrier constituents, said at least one segment and said additional segments being arranged so that predetermined ends of any two consecutive segments are substantially adjacent to one another to avoid time-delay discontinuity in the modulated carrier constituents propagating therethrough. 
     
     
       15. The computerized tomography system of claim 14 wherein each of said individual segments comprises a respective substantially planar transmission line and each respective first and second conductor in said individual segments is substantially parallel to one another. 
     
     
       16. The computerized tomography system of claim 14 wherein said coupler comprises a substantially planar transmission line having first and second conductors aligned substantially parallel to one another and being respectively positioned substantially parallel relative to the first and second conductors of the respective individual segments. 
     
     
       17. In a computerized tomography system having a stationary frame and a generally annular rotating frame, an apparatus comprising: a phase splitter having an input port coupled to receive a modulated carrier having a predetermined bandwidth, said phase splitter having first and second output ports for supplying, respectively, first and second modulated carrier constituents having a substantially 180° out-of-phase angle between one another while maintaining a substantially uniform amplitude over said bandwidth;   a transmission line attached to said rotating frame and positioned substantially around said annular rotating frame, said transmission line comprising at least one individual segment having first and second conductors respectively coupled to the first and second output ports of said phase splitter to receive the first and second modulated carrier constituents from said phase splitter;   a coupler attached to said stationary frame and being positioned sufficiently near said transmission line for establishing radio coupling therebetween so as to receive the first and second modulated carrier constituents being applied to said at least one individual segment; and   a power combiner having first and second input ports for receiving, respectively, the first and second modulated carrier constituents supplied by said coupler, said power combiner being adapted for combining the substantially 180° out-of-phase first and second modulated carrier constituents to form a combined modulated carrier supplied through an output port of said power combiner.   
     
     
       18. The apparatus of claim 17 wherein said power combiner comprises: a first transmission line coupled to the first input port of said power combiner for supplying a respective output signal having a phase angle substantially in-phase with respect to the modulated carrier constituent received through said first input port;   a second transmission line adapted to provide a predetermined level of inductance between the second input port of said power combiner and a predetermined electrical ground, said second transmission line including reversing means coupled to the second output port for supplying a respective output signal having a phase angle substantially 180° out-of-phase with respect to the modulated carrier constituent received though said second input port; and   a combining network comprising first and second combining resistors each having one respective terminal thereof coupled in parallel to the output port of said power combiner, said first and second combining resistors each having another respective terminal respectively coupled to the first and second transmission lines for receiving, respectively, the output signals from the first and second transmission lines.   
     
     
       19. The apparatus of claim 18 further comprising a compensating coil coupled between the first input port of said power combiner and said predetermined electrical ground. 
     
     
       20. The apparatus of claim 18 wherein said combining network further comprises matching resistors for substantially canceling any substantially in-phase input signals received through the first and second input ports of said power combiner. 
     
     
       21. The apparatus of claim 20 wherein said matching resistors comprises a first matching resistor having one respective terminal thereof coupled between the first transmission line and the first combining resistor, said matching resistors further comprising a second matching resistor having one respective terminal thereof coupled between the second transmission line and the second combining resistor, said first and second matching resistors each having another respective terminal thereof coupled to said predetermined electrical ground. 
     
     
       22. The apparatus of claim 18 wherein said first and second transmission lines each comprises a respective coaxial line having a substantially similar electrical length relative to one another. 
     
     
       23. The apparatus of claim 22 wherein each of said coaxial lines comprises a flexible coaxial line wound to form a substantially cylindrical winding. 
     
     
       24. The apparatus of claim 23 wherein said reversing means comprises the outer shield and the center conductor of the coaxial line for said second transmission line, said center conductor being connected to said predetermined electrical ground while said outer shield is connected to the second input port of said power combiner to receive the second modulated carrier constituent. 
     
     
       25. The apparatus of claim 18 wherein said first and second transmission lines comprises a first printed-circuit stage including a respective pair of substantially corresponding conductive strips for each of said transmission lines, respective ones of the respective strip pairs being disposed on mutually opposite surfaces of a first substrate. 
     
     
       26. The apparatus of claim 25 wherein said first and second transmission lines further comprises a second printed-circuit stage including a respective pair of substantially corresponding coils for each of said transmission lines, each respective one of the coil pairs being coupled to a respective one of the corresponding conductive strips in said first stage and being disposed on mutually opposite surfaces of a second substrate. 
     
     
       27. The apparatus of claim 26 wherein each of said mutually opposite surfaces on said second substrate is positioned substantially perpendicular relative to the mutually opposite surfaces on said first substrate. 
     
     
       28. The apparatus of claim 27 wherein said reversing means comprises a feedthrough connector adapted to invert signal flow across each respective one of the pair of substantially corresponding strips for said second transmission line. 
     
     
       29. The apparatus of claim 24 wherein said first and second transmission liens each has a substantially similar electrical length relative to one another. 
     
     
       30. The apparatus of claim 18 wherein the transmission line attached to said rotating frame further comprises additional individual segments each having respective first and second conductors coupled to receive respective first and second modulated carrier constituents, said at least one segment and said additional segments being arranged so that predetermined ends of any two consecutive segments are substantially adjacent to one another to avoid time-delay discontinuity in the modulated carrier constituents propagating therethrough. 
     
     
       31. The apparatus of claim 30 wherein each of said individual segments comprises a respective substantially planar transmission line and each respective first and second conductor in said individual segments is substantially parallel to one another. 
     
     
       32. The apparatus of claim 30 wherein said coupler comprises a substantially planar transmission line having first and second conductors aligned substantially parallel to one another and being respectively positioned substantially parallel relative to the first and second conductors of the respective individual segments.